There’s a deep-freeze of sorts for all good intentions — a place that you store your plans to make changes in your life when you know you’re not going to make them at all. There’s no way of knowing for sure which of your plans are destined for cryopreservation, but when you utter the words “I know I should,” it’s a pretty good bet that you’ve found one.

“I know I should lose weight” too often means you won’t. “I know I should quit smoking” is what you say right before you light up. “I know I should work out more or leave a bad marriage or get out of this lousy job,” are far too often followed by the word, “but.”

And that’s generally the end of it.

The vexing thing about human behavior is that when we say we know we should do something, we really and truly do know it. It’s hard to be 50 lbs. overweight or smoke a pack a day or feel miserable every moment you spend at work and not understand in a deep and primal way that change is in order — and that in some cases it could even save your life. So why do we wind up lost at sea, somewhere between the shores of I-know-I-should and I’m-actually-doing-it?

Dr. Mehmet Oz, who knows a thing or two about motivating people to make life changes, has dug into the recent research and come up with a wealth of recent studies looking at the larger idea of what psychologists call emotional inertia, as well as the strategies — such as incremental goal-setting and group accountability that can get people moving (see his piece in this week’s issue of TIME, available to subscribers here). There’s also the surprising concept of social networks — the way good behaviors like exercising or dieting can be passed along virally from person to person, ultimately among people who may not even know one another at all. Become part of the right web and you can pick up the right habits. Some of this has long been the stuff of support groups, but when the empiricists and scientists start confirming what the life coaches are saying, the arguments become a lot more convincing.

A key part of the new understanding is what’s known as the transtheoretical model, which breaks the business of making changes and adopting new behaviors into five key steps: precontemplation, contemplation, preparation, action and maintenance. There’s probably not a single one of us who hasn’t spent time in all of those stages for any number of life issues. Some of us never move to step five. Some move and then slide back. making real changes means knowing how to make that critical jump from preparation to action, and then, despite all temptation, not to leap back.